1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_
6#define RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_
7
8#include <pthread.h>
9
10namespace base {
11class FilePath;
12}
13
14namespace rlz_lib {
15
16// Creating a recursive cross-process mutex on Windows is one line. On POSIX,
17// there's no primitive for that, so this lock is emulated by an in-process
18// mutex to get the recursive part, followed by a cross-process lock for the
19// cross-process part.
20// This is a struct so that it doesn't need a static initializer.
21struct RecursiveCrossProcessLock {
22  // Tries to acquire a recursive cross-process lock. Note that this _always_
23  // acquires the in-process lock (if it wasn't already acquired). The parent
24  // directory of |lock_file| must exist.
25  bool TryGetCrossProcessLock(const base::FilePath& lock_filename);
26
27  // Releases the lock. Should always be called, even if
28  // TryGetCrossProcessLock() returned |false|.
29  void ReleaseLock();
30
31  pthread_mutex_t recursive_lock_;
32  pthread_t locking_thread_;
33
34  int file_lock_;
35};
36
37// On Mac, PTHREAD_RECURSIVE_MUTEX_INITIALIZER doesn't exist before 10.7 and
38// is buggy on 10.7 (http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906#c34),
39// so emulate recursive locking with a normal non-recursive mutex.
40#define RECURSIVE_CROSS_PROCESS_LOCK_INITIALIZER    \
41  { PTHREAD_MUTEX_INITIALIZER, 0, -1 }
42
43}  // namespace rlz_lib
44
45#endif  // RLZ_LIB_RECURSIVE_CROSS_PROCESS_LOCK_POSIX_H_
46